Measurements before design.

Define the survey

Agree test positions, directions, electrode spacings and site constraints before mobilisation. Buried services, fences, existing electrodes and access restrictions may affect the layout.

Understand the report

The agreed report can include instrument identification, test arrangement, date and conditions, raw resistance readings, apparent-resistivity calculations, observations and limitations. Layered-soil modelling is a separate requirement to specify.

Apparent resistivity—not a guaranteed soil model

The familiar Wenner approximation ρ ≈ 2πaR assumes equal spacing and shallow electrodes relative to spacing. Electrode depth, interference and non-uniform ground require appropriate treatment. A spacing is not an exact depth measurement.

Prepare the site brief

Supply location, layout, test-area dimensions, proposed installation, access and induction requirements, available drawings and required report date. Ask for calibration documentation before mobilisation.

Separate measurement from design

Testing can be appointed on its own, or combined with soil modelling, preliminary earthing concepts, detailed grid design, installation review and commissioning. State the required decision and deliverable in the enquiry so the quotation is comparable.

Testing alone does not certify the completed earthing system. Design, installation verification, fault studies and touch/step assessment must be expressly included where required.